Beaglebone Black Serial c++ - c++

Question

It seems to be a pain to get serial working in c++, adding to that, to do it on the Beaglebone Black is hard, so I need someone with some expertise!
I created /dev/ttyO4 with the following command:
echo BB-UART4 > /sys/devices/bone_capemgr.9/slots
This gives me /dev/ttyO4. I then write a small program in cpp using a library linked here. My code is found below:
#include <stdio.h>
#include "serialib.h"
#if defined (_WIN32) || defined( _WIN64)
#define DEVICE_PORT "COM1" // COM1 for windows
#endif
#ifdef __linux__
#define DEVICE_PORT "/dev/ttyO4" // ttyS0 for linux
#endif
int main()
{
serialib LS; // Object of the serialib class
int Ret; // Used for return values
char Buffer[128];
// Open serial port
Ret=LS.Open(DEVICE_PORT,115200); // Open serial link at 115200 bauds
if (Ret!=1) { // If an error occured...
printf ("Error while opening port. Permission problem ?\n"); // ... display a message ...
return Ret; // ... quit the application
}
printf ("Serial port opened successfully !\n");
// Write the AT command on the serial port
Ret=LS.WriteString("AT\n"); // Send the command on the serial port
if (Ret!=1) { // If the writting operation failed ...
printf ("Error while writing data\n"); // ... display a message ...
return Ret; // ... quit the application.
}
printf ("Write operation is successful \n");
// Read a string from the serial device
Ret=LS.ReadString(Buffer,'\n',128,5000); // Read a maximum of 128 characters with a timeout of 5 seconds
// The final character of the string must be a line feed ('\n')
if (Ret>0) // If a string has been read from, print the string
printf ("String read from serial port : %s",Buffer);
else
printf ("TimeOut reached. No data received !\n"); // If not, print a message.
// Close the connection with the device
LS.Close();
return 0;
}
When I run the code, it says it opened the port successfully and successfully wrote serially, but I receive no data on the RX. I have connected the RX pin to the TX pin for UART4 (P9.11 and P9.13). I also connected the RX and TX pins for UART5 just incase (P8.37 and P8.38), as the ttyO4 confused me a bit as to which UART I'm using.
Is there something I'm missing to get the serial port working? Or can someone refer me to a working example for serial communication with c++ on the beaglebone black, perhaps like a step-by-step guide?
Regards,
Cornel
EDIT:
The Boost serial libraries work more reliably than serialib, find them here.

Answer 1

So I tried the same steps as you did. I downloaded and compiled the code from http://serialib.free.fr/html/classserialib.html and compiled with a warning about
serialib.cpp: 337:40: warning: converting to non-pointer type 'unsigned int' from NULL [-Wconversion-null]
(If you know how to fix this please let me know). But I ran the program with the Tx/Rx pins hooked up to an Arduino Mega Rx1/Tx1 pins. The program writes fine and I can see the Arduino read in the bytes. When I write from the Arduino to the Rx of the Beaglebone Black it times out and says no data was received.
As far as I can tell, this is a problem with how the Rx pin is set.
EDIT: So I just printed the Buffer that receives the data written to the port and it receives the data just fine. So the problem is with the value of Ret. For now you can use the buffer as the received data. I'll try and figure out why the return value from ReadString() isn't working.

Answer 2

to correct the [-Wconversion-null] error:
Open 'serialib.cpp' file and go to the 'ReadStringNoTimeOut' function.
Change
ret=ReadChar(&String[NbBytes]);
to
ret=ReadChar(&String[NbBytes],0);